Approximately 3.6 million people in the US and Europe (Lotus, E. (2004) Gastroenterol. 126: 1504-1517) and about 15.8 million people worldwide have inflammatory bowel disease or IBD (Lakatos, P. (2006) World J. Gastroenterol. 12(38): 6102-6108). IBD is a collective term used to describe two gastrointestinal disorders of unknown etiology; Chron's disease (CD) and ulcerative colitis (UC). Both diseases appear to result from the unrestrained activation of an inflammatory response in the intestine. Ulcerative colitis occurs in the large intestine, while Chron's disease can involve the entire gastrointestinal tract, as well as the small and large intestines. It has been suggested that the pathogenesis of IBD is multifactorial involving susceptibility genes and environmental factors Sartor et al. (1997) Am. J. Gastroenterol. 92: 5S-11S. Although the causative triggers remain unclear, the role of a persistent and likely dysregulated mucosal immune response is central to the pathogenesis of IBD. It remains unclear whether the persistent inflammation, an intrinsic feature of IBD, reflects a primary aberration in mucosal response or results from an inappropriate persistent stimulation. Curr. Opin. Gastroenterol. (2003) 19(4): 336-342. The course and prognosis of IBD varies widely. For most patients, it is a chronic condition with symptoms lasting for months to years. IBD is most common in young adults, but can occur at any age. The clinical symptoms of IBD include intermittent rectal bleeding, fever, abdominal pain, and diarrhea, which may range from mild to severe. Additional common signs of IBD are anemia and weight loss. 10 to 15% of all IBD patients will require surgery over ten year period. Protracted IBD is a risk factor for colon cancer, and the risk begins to rise significantly after eight to ten years of IBD.
The first line therapy that is often used for IBD is aminosalicylates, which include sulfasalazine and the brands Asacol, Pentasa, Dipentum, and Colazal. Treatment for Chron's disease takes a stepwise approach with nutritional supplements and 5-ASA often used as chronic therapy aimed at prophylaxis against flare-up of the disease. Some physicians believe that 5-ASAs are not effective in CD and start with a steroid such as budesonide. When mild to moderate patients flare up, they are often treated with a short course of steroids. For more severe patients or those with more frequent flares, immunosuppressices such as azathioprine (Imuran), 6-MP, and methotrexate are used. The anti-TNF antibody Remicade is also used to treat Chron's disease. Treatment of ulcerative colitis is very similar to treatment of Chron's disease, following a similar stepwise approach with the use of 5-ASAs, short courses of steroids, other immunosuppressives and surgery. Remicade is sometimes used for severe disease not responding to steroids or traditional immune modulators. Methotrexate and antibiotics are generally not used in UC and it's believed by many physicians that methotrexate does not work in UC. Need for surgery is more prevalent in UC than in CD, with 25-40% of patients eventually requiring colectomy. Unlike in Chron's disease, surgery for ulcerative colitis is curable. There are unmet needs for IBD patients who fail on all of the currently available therapies. Approximately 20% of patients fail all therapies and need surgery in the short term, 40% of patients will require surgery in the long term.
Irritable bowel syndrome, or IBS, is the most prevalent digestive disease, accounting for 12% of visits to primary care physicians and 28% of referrals to gastroenterologists. IBS is one of a heterogeneous family of functional gastrointestinal disorders, which are difficult to treat because no single etiology for these disorders is known and thus treatment is directed at controlling symptoms. IBS affects at least 10 to 20% of adults in the US, mostly women, and second only to the common cold as a cause of absenteeism from work. The majority of cases are undiagnosed because only 25-30% of patients seek medical attention (International Foundation for Functional Gastrointestinal Disorders). IBS produces disability rates equal to or greater than severe organic gastrointestinal disease. One study reported that 8% of patients with IBS retire early due to their symptoms. Rees, G. et al. (1994) J. R. Soc. Health 114: 182. IBS is characterized by altered bowel habits and abdominal pain, typically in the absence of detectable structural abnormalities. No clear diagnostic markers exist for IBS, and its definition is based on its clinical presentation. IBS is often confused with IBD, colitis, mucous colitis, spastic colon, or spastic bowel. Only recently physicians started considering IBS to be a brain-gut functional disorder, rather than a somatic manifestation of physiological stress. The Rome diagnostic criteria of IBS (currently, Rome II) can be used to rule out other disorders. According to the Rome II criteria, abdominal pain or discomfort is a prerequisite clinical feature of IBS. Drossman D. et al. (eds) Rome II: the functional gastrointestinal disorders: diagnosis, pathophysiology, and treatment: a multinational consensus. McLean, V A: Degnon Associates, 2000. Most IBS patients experience several IBS symptoms such as abdominal pain, altered bowel habits, flatulence, upper GI symptoms such as dyspepsia, heartburn nausea, and vomiting. IBS patients typically fall into two broad clinical groups. Most patients belong to the first group, presenting with abdominal pain associated with altered bowel habit that include constipation diarrhea or alternating constipation and diarrhea. The second group of patients have painless diarrhea. It is generally believed that the central nervous system plays an important role in the pathogenesis of IBS. This is supported by the clinical association of emotional disorders and stress with IBS symptom exacerbation, and the therapeutic response to IBS therapies that act on cerebral cortical sites.
About 80% of IBS patients are treated with some form of therapy. The management approach for IBS depends on the patient's predominant symptoms. The goal in patients with constipation-predominant IBS (IBS-C) is to stimulate a bowel movement, thus, bulk fiber laxatives can be used several times per day. Second line therapy may involve Senekot and antispasmodics (e.g., Levsin) for periodic cramping and abdominal pain. Third line therapy may include Zelnorm. Usually, 40% of patients with IBS-C improve with treatment. In patients with diarrhea-predominant IBS, lactose intolerance and bacterial overgrowth must be ruled out first. Imodium is standard treatment for this type of IBS. Lotronex is rarely used and reserved only for the very severe patients due to risk of ischemic colitis. 60% of diarrhea-predominant IBS (IBS-D) patients improve with treatment. Patients with mixed-symptom IBS (IBS-A) may be treated with a combination of approaches depending on whether the patient is experiencing a period of constipation or diarrhea. A portion of these patients are also likely to be IBS-D or IBS-C patients that get overmedicated and swing to the other extreme. Most long-term studies of IBS report that symptoms persist for more than five years in greater than 75% of patients despite appropriate therapy.
Bowel disorders such as IBD and IBS are a medical problem, and improved methods of treatment are necessary as no satisfactory treatments are currently available.